The present invention relates a valve spring retainer and a valve operating mechanism in an internal combustion engine.
FIG. 10 is one example of a conventional valve operating mechanism in an internal combustion engine, in which a valve spring retainer 3 is mounted at the upper end of a poppet valve 1 by a pair of cotters 2,2. A valve spring 4 is provided between the lower surface of an outer flange 3a of the valve spring retainer 3 and a cylinder head (not shown), so that the poppet valve 1 is always energized upwards by the valve spring 4.
The numeral 5 denotes a rocker arm which is engaged on the axial end of the poppet valve 1 and which is moved up and down by a rotary cam (not shown), so that the poppet valve 1 is opened and closed.
The flange 3a of the valve spring retainer 3 of the valve operating mechanism has a horizontal lower surface perpendicular to an axis of the valve spring retainer 3, and is adapted to contact the upper surface of the valve spring 4 when the valve spring 4 is equipped.
It is inevitable to wear the lower surface of the flange 3a of the retainer 3 owing to relatively rotational or radial movement of the valve spring 4 caused by vibration when the poppet valve is seated.
Especially, in an automobile engine which is accelerated or decelerated frequently, as illustrated in FIG. 11, when the valve spring 4 is compressed, the uppermost winding is twisted outwards as shown by a downward arrow, or the flange 3a is bent upwards by reaction force to compression as shown by an upward arrow when the valve spring 4 is compressed.
In the conventional valve spring retainer 3 in which the lower inner surface of the flange 3a is horizontal, the inner upper circumference of the first winding which is horizontal at the upper end of the valve spring is engaged with the lower surface of the flange 3a, so that a larger surface pressure is applied.
Thus, as shown in FIG. 12, at the beginning of operation, the lower inner portion of the flange 3a locally wears, and develops outwards as shown by dotted lines. Especially, in the valve spring retainer 3 made of Al alloy for decreasing weight, wear develops rapidly.
Also, owing to vibration in opening and closing of the poppet valve 1 or surging in the valve spring 4, the flange 3a of the retainer 3 is rotated with respect to the valve spring 4, thereby causing contact surfaces to wear away. Especially, in the Al alloy valve spring retainer 3 for lightening, wear to the valve spring retainer 3 becomes larger.
As wear becomes larger, setting load of the valve spring 4 becomes smaller to decrease the maximum rotation speed of surging, thereby decreasing engine performance. Depending on degree in wear, it becomes necessary to replace the retainer 3 with a new one.
In view of the disadvantages in the prior art, it is an object of the present invention to provide a valve spring retainer in which the lower surface of a flange is modified in shape to decrease wear, thereby increasing durability and reliability.
It is another object of the present invention to provide a valve operating mechanism of an internal combustion engine in which a valve spring retainer is prevented from rotation with respect to a valve spring to keep wear of the contacting surfaces at minimum.